The present invention generally relates to prosthetic foot devices. More particularly, the present invention relates to a prosthetic foot having a ground-engaging base with at least one flexible hinge and a spring structure to simulate the performance of natural foot movement.
Many individuals have lost a limb for various reasons including war, accident, or disease. In most of these instances, these individuals are aided in their everyday lives by a prosthetic limb. The objective of prosthesis is to provide an artificial limb that simulates the function and natural feel of the replaced limb.
Artificial limbs and particularly prosthetic feet and legs have been known for centuries. The earliest were probably similar to the crude wooden “peg legs”. These early devices enabled the user to stand and to walk awkwardly, usually with the additional aid of a crutch or cane. Over time, designers of artificial or prosthetic feet attempted to duplicate the appearance and function of a natural foot. The development of a functional and natural artificial foot has been limited only by material and imagination. Various types of foot and leg prosthetic devices are well-known in the prior art. Such devices generally include some form of attachment for coupling the device to the dorsal end of the limb and for extending to the ground to provide body support. Normally, the prosthetic device is strapped to the limb to keep the prosthetic device in place throughout the wearers normal motion, particularly when lifting the limb for walking and the like.
Many designs have attempted to copy the anatomy of the foot or simulate its action by replacing the bones and muscles with various mechanical components. Designers have attempted to closely approximate the action of natural foot by adding ball and socket ankle joints geometrically similar to a natural anatomical ankle. However, without all the muscles, tendons and cooperating bone structure of an anatomical foot, the anatomical type ankle joint is too unstable to be practical. Moreover, another problem with such configurations is the complexity of the several joints. There are numerous moving parts and joints subject to friction, wear, and failure.
Other designs have departed radically from mere anatomical copying and mechanical simulation by replacing the entire foot with an energy storage element such as a spring. Various prosthetic feet in the prior art have been designed with spring components and tend to store energy when the foot is placed on the ground and to releases it and provide a lift or thrust as the foot is removed from the ground again to aid in the patient's gait and propel the user forward.
However, no prosthetic foot in the prior art has been completely successful in approximating the performance and response of a natural foot. Those prior art prosthetic feet which did not utilize a spring-loaded heel experienced a lag or deadness after the user placed the heel on the ground and began to roll the foot forward during the gait cycle. This was due to the necessity of loading a spring in the toe section after the user's weight had been placed on the ground. The response and feel of a natural foot cannot be achieved unless the springs are loaded as the user's weight is placed on the ground rather than after. Other prior art prosthetic feet utilize a spring-loaded heel which operated on the spring separate from the springs in the toe section effectively stored energy in the heel, but were ineffective in transferring energy from the heel to the toe portion of the prosthetic foot as the foot rolled forward during the gait cycle. These devices still required separate loading of the spring in the toe section. As a result, the user noticed a distinct and unnatural lag or hesitation in rolling the foot forward during the gait cycle, giving the foot an unnatural feel and possibly causing an uneven stride.
One-piece spring devices experienced a lag or deadness after the patient placed the heel on the ground and began to roll forward because the spring design was not suited to absorb and store sufficient energy in the heel and then transfer it to the toe section, thus requiring the toe section to be loaded after the patient's weight had been placed on the ground. Such dead or flat spots are particularly noticeable when navigating steps or walking backwards. Oftentimes, users wearing a prosthetic foot would hang at least a portion of the prosthetic foot over the stair and then roll the foot over the stair in a leverage manner, similar to a teeter-tauter, to navigate the stair as the user descends.
Nearly all of the past designs have focused on the major aspect of the prosthetic foot, that is movement of the ankle or foot as it relates to walking or running. Very few designs have considered the workings of the toes or less conspicuous movements of the foot and ankle when the user navigates an incline, decline or uneven terrain. The prosthesis of the previous designs usually incorporate a unitary foot and toe platform that is incapable of such independent rotational movement or response. Thus, the users were required to dig the toe or heel into the decline or incline to provide sufficient stability to navigate the same. When experiencing uneven terrain, such as rocks, the prosthetic foot was unable to navigate such obstacles and often caused tension or even hyperflexion of the user's knee or hip.
Accordingly, there is a continuing need for an improved prosthetic foot which better simulates the fluid movement and natural gait of a real foot. Such a prosthetic foot should provide fluid movement without dead or flat spots. Such prosthetic foot should also conform to irregular surfaces, inclines and declines. Such prosthetic foot should not be very complex in design nor costly. The present invention fulfills these needs and provides other related advantages.